You need to define the power button in the power options for this.
Just head to the power options, you can go to the power options by simply right-clicking the battery icon on your system tray or you can also go there by going to the control panel.
Then inside the power options, just choose what the power buttons do.
Then under the define power buttons and turn on password protection, you will see some options for power and sleep buttons and lid settings.
Then here you need to set the first option which says when I press the power button, choose to turn off display from the drop-down menu.
That is it, it is that simple to use the regular power button for yourself and to make it useful for you. You can thus turn off laptop screen using your laptop power button.
ScreenOff is a first-of-its-kind 13KB freeware that lets you turn off your Windows laptop monitor screen in a click, without putting it to Sleep. This tool does not use a batch command. It uses a SendMessage Visual Basic command to send the system, the command to turn off the display. Moreover, it is a portable tool that does not require to be installed. Nor does it ask you to download and install any specific .NET Framework version.
Simply download the zip file, extract its contents, move the folder to your Program Folder and pin the shortcut of ScreenOff.exe to your Start Screen or Taskbar.